Showing papers on "Precipitated silica published in 2011"

Impact of Filler Surface Modification on Large Scale Mechanics of Styrene Butadiene/Silica Rubber Composites

Abstract: In material science of elastomers the influence of nanoscale and nanostructured filler particles is of utmost significance for the performance of innovative rubber products, i.e., passenger car tires with ultralow rolling resistance but high wet-grip performance. A better understanding of the physical characteristics of the filler–rubber interface and the filler–rubber interphase as well is necessary to improve the overall macroscopic properties of these elastomeric nanocomposites. Therefore, the surface energies and polarities of filler particles with different modified surfaces were measured by a modified Wilhelmy technique. In all cases the rubber matrix consisted of a solution - styrene butadiene copolymers, filled with 20 or 40 phr pyrogenic or precipitated silica grades with different surface modifications by silanes, and a carbon black sample as reference. A moving die rheometer was employed to observe the filler flocculation at elevated temperatures (160 °C) in rubber mixtures containing no curati...

Fluoroalkyl-Functionalized Silica Particles: Synthesis, Characterization, and Wetting Characteristics

Abstract: Fluoroalkyl-functionalized silica particles for use in nonwetting surfaces were prepared by treatment of silica particles with fluoroalkyl-functional chlorosilanes. Both fumed and precipitated silica were studied, as well as the efficiency of surface coverage using mono-, di-, and trifunctional chlorosilanes. The most effective surface treatment was accomplished via the surface grafting of monofunctional chlorosilanes in the presence of preadsorbed dimethylamine under anhydrous conditions at room temperature. Confirmation of covalent attachment was accomplished via Fourier transform infrared (FT-IR) spectroscopy, while elemental analysis, thermogravimetric analysis, and nitrogen adsorption isotherms were used to determine grafting densities and additional key geometric characteristics of the grafted layer. The effect of residual silanol content on the moisture uptake properties of the modified silica particles was determined by measuring the water uptake of unbound particles, while liquid wetting properti...

Silica precipitation with synthetic silaffin peptides

Abstract: Silaffins are highly charged proteins which are one of the major contributing compounds that are thought to be responsible for the formation of the hierarchically structured silica-based cell walls of diatoms. Here we describe the synthesis of an oligo-propyleneamine substituted lysine derivative and its incorporation into the KXXK peptide motif occurring repeatedly in silaffins. Ne-alkylation of lysine was achieved by a Mitsunobu reaction to obtain a protected lysine derivative which is convenient for solid phase peptide synthesis. Quantitative silica precipitation experiments together with structural information about the precipitated silica structures gained by scanning electron microscopy revealed a dependence of the amount and form of the silica precipitates on the peptide structure.

Synthesis and Characterization of Nylon-6/Mesoporous Silica Nanocomposites via In Situ Synchronous Hydrolytic Polymerization of Tetraethylorthosilicate and ε-Caprolactam

Abstract: Nylon 6 (N6)/mesoporous silica (MS) nanocomposites (NMSNs) were synthesized via in situ synchronous hydrolytic polymerization of tetraethylorthosilicate (TEOS) and e-caprolactam. The novelty of this technique lies in that the nanosilica generated in situ has unique mesoporous structure and ultrahigh-specific surface area (SSA). Mechanical test showed that, compared to conventional precipitated silica (PS) nanofillers, the MS generated in situ shows better reinforcing efficiency on N6. At a loading of only 3.0 wt % MS, the tensile modulus, flexural modulus, and the heat distortion temperature of NMSNs exhibit increase of 54.8%, 77.9%, and 55.9°C, respectively. The effects of MS on the crystallization behaviors of N6 have been studied by differential scanning calorimetry (DSC), which shows that the incorporation of MS influences the crystallization behaviors of N6 obviously: (1) increases crystallization temperature (Tc) by serving as heterogonous nucleating agent; (2) favors the formation of γ-phase by hindering the mobility of N6 chains. Dynamic mechanical analysis confirmed that, compared ti that of neat N6, the temperature of the main α-relaxation (Tα) and the secondary β-relaxation (Tβ) of NMSNs is shifted 6.1°C and 5.3°C toward higher temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Novel method for preparing precipitated silicas containing aluminium

Abstract: The invention relates to a method for preparing precipitated silicas, comprising a precipitation reaction between a silicate and an acidifying agent, thereby producing a precipitated silica suspension, and, subsequently, the separation and drying of said suspension, in which, inter alia, one of the following three operations (a, b or c) is performed: (a) simultaneously adding a compound of aluminium and a basic agent, (b) simultaneously adding a silicate and a compound of aluminium, (c) simultaneously adding the acidifying agent, a silicate and a compound of aluminium.

Fly ash particles and precipitated silica as fillers in NR/CR vulcanizates under thermal and thermal-oil ageing

Abstract: The loading effect of precipitated silica (PSi) and fly ash-based silica (FASi) on mechanical properties of natural rubber/chloroprene (NR/CR) under thermal and thermal-oil ageing was investigated with variation in NR content in the NR/CR blends. The selected results were compared with vulcanized NR/nitrile rubber (NR/NBR) blends. The cure time of CR vulcanizate was found to decrease with increasing NR content, but increased with silica fillers. The Mooney viscosity for CR vulcanizates reduced with increasing NR content. The addition of NR had no effect on tensile modulus and tensile strength for the FASi filled NR/CR, but the opposite trend was observed for the PSi filled NR/CR. The post-curing effect was more significant in PSi filled NR/CR than in FASi filled NR/CR. The tensile strength of the NR/CR vulcanizates was slightly reduced after thermal ageing especially at high NR content, more extreme reduction being found by thermal-oil ageing. The elongation at break of NR/CR with both silica fillers ranged from 400 to 900%. The hardness results were similar to the tensile modulus. The addition of PSi in NR/CR considerably increased the tear strength, but less pronounced effect was found for FASi. The resilience properties of NR/CR tended to decrease with increasing silica content. The compression set became poorer when NR content was increased. The PSi showed higher improvement in compression set than the FASi. The effects of silica and ageing on the mechanical properties for NR/CR vulcanizates were similar to those for NR/NBR vulcanizates. Copyright © 2009 John Wiley & Sons, Ltd.

Precipitated silica production process

Abstract: The invention relates to a precipitated silica production process that includes a precipitation reaction between a silicate and an acid, in which the acid used in at least one of the steps of the process is a concentrated acid.

Precipitated Silica from Wheat Husk

Abstract: In present investigation extraction of amorphous silica from wheat husk and then converting it into precipitated silica by using sodium hydroxide has been studied at various Na/Si ratios and reaction time. Wheat husk was calcined in electric tube furnace at 500 0 C for two hours to produce wheat husk ash (WHA). XRD of WHA confirmed its amorphous nature. The WHA was treated against sodium hydroxide at different molar ratios and reaction time to obtain sodium meta silicate. Each time sodium meta silicate was treated against 0.1N HCl to recover silica in precipitated form. XRD and FTIR results confirmed the amorphous nature of precipitated silica. It was also observed that one hour boiling with molar ratio Na/Si =2 is sufficient for optimum conversion into sodium meta silicate.

Use of precipitated silica containing aluminium and 3-acryloxy-propyltriethoxysilane in an isoprenic elastomer composition

Abstract: The invention relates to the joint use, in an elastomer composition comprising an isoprenic elastomer, of a precipitated silica containing aluminium, as a reinforcing inorganic filler, the aluminium content of said precipitated silica being higher than 0.5 wt. %, and 3-acryloxy-propyltriethoxysilane as an inorganic filler - elastomer coupling agent. The invention also relates to the elastomer compositions obtained and the items produced from said compositions.

Analysis of mercury porosimetry curves of precipitated silica, as an example of compressible porous solids

Abstract: Mercury intrusion curves in a series of silica samples are analyzed, together with the study of nitrogen adsorption/desorption curves and TEM pictures. A detailed discussion of the mechanisms that operate during the mercury intrusion is presented, identifying several steps: elastic sample compression, plastic sample compression and mercury intrusion. A mathematical model of the plastic sample compression is presented and applied to these silica samples. The pore size of the maxima in mercury intrusion is smaller than that calculated by the BJH method applied to nitrogen desorption. The differences are explained by accounting for the sample compression and the differences in the mechanism in both techniques.

Use of Antioxidant-modified Precipitated Silica in Natural Rubber

Abstract: Fillers play a dominant role in modifying the properties of the base polymer. Precipitated silica is a promising non-black filler for rubber vulcanisates. As silica is hydrophilic and rubber is hydrophobic, uniform dispersion of silica in rubber is difficult and gives rise to problems such as high initial viscosity. Silica has a number of hydroxyl groups, which result in filler―filler particle agglomeration and reagglomeration. Incorporation of silica into rubber is quite difficult compared with the incorporation of carbon black. The main aim of this study was to reduce the hydrophilicity of silica by coating antioxidant onto its surface, and hence achieve easy incorporation of silica into rubber. The preparation of antioxidant-modified precipitated silica and its use as filler in rubber compounds were investigated. The curing and mechanical properties of the compounds were compared with those of conventional compounds containing unmodified silica and antioxidant in the same dosage on natural rubber. The cure and mechanical properties were found to be superior for modified silica composites compared with unmodified silica composites.

Platinum catalysts supported on silicas: effect of silica characteristics on their catalytic activity in carbon monoxide oxidation

Abstract: Platinum catalysts supported on silicas with various physicochemical properties were prepared in order to investigate the effect of silica characteristics on their platinum dispersion and catalytic activity in the oxidation of carbon monoxide. Although titania-incorporation into silica and further treatment of the impregnated platinum precursor with hydrogen peroxide were effective for improving the dispersion and stability of platinum catalysts supported on silicas, regardless of the characteristic of the silicas, the platinum catalysts supported on fumed silica with a medium level of surface hydroxyl group concentration exhibited the highest catalytic activity among those supported on mesoporous silica, silica gel, and precipitated silica. The required properties of the highly active platinum catalyst seemed to be a high dispersion of platinum, the formation of a stable titania layer, and the generation of strong acid sites. By contrast, the precipitated silica with a small surface area and high concentration of surface hydroxyl groups was not appropriate for a catalytic support for platinum catalysts.

Polyurethane resin prepolymer solution and artificial leather fog washing bright finishing agent prepared by using same

Abstract: The invention discloses a polyurethane resin prepolymer solution which is prepared from the following raw materials in parts by weight: 5-10 parts of hydroxyl-terminated fluoropolysiloxane, 20-30 parts of toluene diisocynate (TDI), 20-30 parts of polyester polyol, 1-5 parts of ethylene glycol (EG), 20-30 parts of dimethylformamide (DMF), 20-25 parts of toluene, 3-5 parts of acetone and 1-2 parts of organic tin catalyst The invention also discloses an artificial leather fog washing bright finishing agent prepared by using the polyurethane resin prepolymer solution The finishing agent is prepared from the following raw materials in parts by weight: 20-60 parts of the fluoropolysiloxane modified polyurethane resin prepolymer solution, 2-10 parts of Teflon wax powder, 2-10 parts of precipitated silica or fumed silica, 10-30 parts of dimethylformamide and 20-30 parts of toluene

Consolidation of Inorganic Precipitated Silica Gel

Abstract: Colloidal gels are possible intermediates in the generation of highly porous particle systems. In the production process the gels are fragmented after their formation. These gel fragments compact to particles whose application-technological properties are determined by their size and porosity. In the case of precipitated silica gels, this consolidation process depends on temperature and pH, among other parameters. It is shown that these dependencies can be characterized by oedometer measurements. Originally, the oedometer test (one-dimensional compression test) stemmed from soil mechanics. It has proven to be an interesting novel examination method for gels. Quantitative data of the time-dependent shrinkage of gel samples can be obtained. The consolidation of the gels shows a characteristic dependence on the above parameters.

MCM-41 Porosity: Are Surface Corrugations Micropores?

Abstract: Since the discovery of MCM-41, the interpretation of its structure and porous texture has evolved from a simple model of straight parallel mesopores to a much more complex model with a rough surface. The physisorption of nitrogen at 77.3 K and 87.5 K and of carbon dioxide at 273 K was carried out on both MCM-41 and a precipitated silica (PSIL). This silica was prepared for comparison purposes under identical conditions to those for MCM-41 but without the use of the surfactant. The adsorption characteristics of both materials for both adsorptives were indistinguishable at low adsorption pressures independent of the adsorption temperature employed, suggesting similarities in parts of their porosity (i.e. excluding mesoporosity). We propose that, in addition to its well-acknowledged mesoporosity, MCM-41 includes considerable surface roughness and/or heterogeneities similar to that shown by microporous silica. This surface structure appears to have adsorption characteristics indistinguishable from classical m...

Stable aqueous dispersions of precipitated silica

Abstract: The invention relates to stabilized dispersions of precipitated silicon dioxide, to a process for production thereof and to the use thereof, especially for production of paper coatings for glossy photo paper for inkjet printing

γ-Radiation Induced Functional Modification of Silica and Radiation Vulcanization of SBR-Silica Composites

Abstract: Summary: The γ-ray induced “grafting” of polybutadiene olygomers onto precipitated silica and the radiation induced crosslinking of the blends prepared with the modified silica in SBR matrices have been investigated in the dose range up to 290 kGy. Enhanced mechanical properties have been detected for the SBR blends containing the modified silica after γ-ray induced crosslinking. The comparison with the analogue mixtures containing pristine silica, supported by EPR measurements, suggests that the PB coating is effective in enhancing the mechanism of formation of filler-rubber chemical links.

Application of Precipitated Silica in Low Basis Weight Newspaper

Abstract: Filler is one of the most important components of paper. Silica is a kind of excellent filler for its special chemical structure. Silica was prepared in the laboratory, and applied into paper. The dispersion properties of the silica with different sizes in paper sheets, the effect of smash on dispersion property of silica in paper sheets, the effect of silica on the zeta potential of newspaper pulp system, the effect of retention agent cationic polyacrylamide on zeta potential of newspaper pulp system and the effect of silica on properties of paper sheet were measured. The results show that the fineness of the silica used in paper is the most important factor which affects the dispersion. The addition of silica and the use of retention agent cationic polyacrylamide increase the zeta potential of the newspaper pulp system. The addition of precipitated silica increases the whiteness of paper slightly and the opacity obviously.

New methods to analyse fragmentation mechanisms of precipitated silicas

Abstract: Precipitated silica is traditionally used as reinforcing filler in rubber applications. In pneumatic manufacture, it offers several advantages compared to carbon black. Indeed, in tyres treads, precipitated silica can yield a lower rolling resistance and better wet grip at equal wear resistance than carbon black. The development of a new method to study the fragmentation mechanism of precipitated silica is investigated. Usually, the dispersion of granules is done in high viscous media (elastomer or oils). In this paper, the study is carried out in a friendlier medium (air or water).

Effects of silica on the rheological and mechanical properties of the RTV silicone rubber foam

Abstract: Room temperature vulcanization(RTV) silicone foam materials have been prepared by using five kinds of silica as reinforcing fillers.The effects of silica by different preparation methods and surface modification on the rheological property and foam mechanical properties of the based-compound during the silicone foam preparation were investigated in detail.The results indicated that the curing rate of the based-compound filled with the hydrophobic silica was faster than that filled with the hydrophilicity silica,in case of the same weight addition of the silica;the curing rate increased as the content of the fumed silica increased,whereas the curing rate decreased as the precipitation silica increased;the dispersity of the precipitated silica in the silicone rubber matrix is inferior to that of the fumed silica with hydrophobic modification.As the silica content increased,the holes size of the silicone rubber foam materials became smaller while the tensile-strength of them improved.

Bleed Resistant, Oil-Extended Olefin Block Copolymer Composition with Precipitated Silica

Abstract: Disclosed are oil-extended olefin block copolymer compositions with precipitated silica. The precipitated silica reduces oil-bleed while maintaining composition softness.

Highly transparent electronic encapsulating adhesive

Abstract: The invention relates to the field of silica gels, in particular to a highly transparent electronic encapsulating adhesive with high light transmittance and low production cost The adhesive is prepared by the following production steps of: 1) preparing hydroxyl-terminated polydimethylsiloxane, namely base polymer; 2) performing surface treatment on a reinforcing filler; 3) performing internal mixing to prepare a semi-finished adhesive; and 4) preparing a finished highly transparent electronic encapsulating adhesive The invention has the advantages that: a production formula and a process are technically innovated, the conventional expensive fumed silica is discarded, precipitated silica is adopted and is subjected to surface modification by a composite treating agent (silazane, methoxysilane, hydroxyl silicone oil, water and the like) after being subjected to nano-scale dispersion so as to form an 820# electronic encapsulating adhesive with the light transmittance of 96 percent, and the light transmittance is 4 percent higher than that of the product prepared by the conventional process, namely the light energy utilization rate of components on an encapsulating surface is improved by 4 percent; and the light utilization rate is improved, namely the production cost of a part is reduced, and an obvious progress is made

Preparation of precipitated silica from desilicated solution of high-alumina fly ash by dissolution with alkali:experiment and principle of polymerization of silicic acid

Abstract: In this paper,high-alumina fly ash from a thermal-electric plant of Shaanxi Province was used as raw material,and was treated with alkali to prepare desilicated solution,which was then carbonated to prepare precipitated silicaDuring orthogonal experiments and single-factor experiments,the optimal carbonation conditions were determined as follows,under 100 r·min-1 speed stirring,500 ml·min-1 CO2 flow rate,sodium metasilicate concentration 178°Be,and at reaction temperature around 85℃,reaction time around 25 hThe white carbon black product(BTH-01)was prepared from silica gel through drying at 105℃ overnightThe product(BTH-01)satisfied the type A standard of white carbon black GB10517—89The carbonation reaction process was analyzedNuclear magnetic resonance measurement method was used to trace the processing path of silica gel,which could better describe the Si—O conjugation during different times in carbonationThe technology provides some guidance to analyzing the structure of white carbon black

Method for producing finely powdered silica and apparatus for producing the same

Abstract: PROBLEM TO BE SOLVED: To make silica made from a natural product occurring in nature still finer.SOLUTION: There is provided a method for producing finely powdered silica comprising forming a silica-containing solution formed by dissolving precipitated silica derived from a natural product in carbon dioxide in a silica-containing solution formation tank 23, compressing the silica-containing solution by means of a compressor 24, thereafter ejecting the compressed silica-containing solution through an ejection mechanism 25 to effect its rapid pressure reduction and expansion to thereby evaporate the carbon dioxide from the solution, and recovering the finely powdered silica in a finely powdered silica recovery tank 26.

Processibility and Mechanical Properties of Mullite-Filled Styrene Butadiene Rubber Composites

Abstract: Mullite (3A12O3·2SiO2) is an aluminosilicate ceramic of great technological importance. We investigated its potential as fillers in rubber. Mullites untreated or treated with 3% γ-mecapto-propyltrimethoxysilane (A-189) were added into styrene-butadiene rubber (SBR) materials on a laboratory-sized two-roll mill. For comparison, commercial precipitated silica was also used. The effect of these fillers on the cure characteristics, processibility and mechanical properties of SBR at various loadings, ranging from 0 to 50 phr was investigated. The results showed that mullite was a semi-reinforcing filler for SBR materials and exhibits better overall cure properties, lower Mooney viscosity, lower tensile set, better resilience as compared to precipitated silica, while it is inferior to precipitated silica especially with regard to tensile strength, tear strength and abrasion resistance. The presence of the silane coupling agent can enhance mechanical properties of filled SBR vulcanizates to some extent.

Effect of Vinyltriethoxysilane Content on Mechanical and Physical Properties of Precipitated Silica Reinforced Silicone Rubber

Abstract: 실리카의 표면 개질제인 vinyltriethoxysilane(VTEOS)의 함량에 따른 실리카로 보강된 실리콘 고무의 기계적 물성 변화 및 내열성, 내유성, 압축 영구줄음률, 반발탄성 및 가교밀도 변화를 연구하였다. 결과로 VTEOS의 함량이 2.0 phr까지 증가함에 따라 경도는 상승하였으나 인장강도, 파단신율, 인열강도가 감소하였다. 내열시험에서는 VTEOS의 함량이 증가될수록 경도변화, 인장강도 변화율, 파단신율 변화율이 크게 감소하였다. VTEOS 2.0 phr에서 가장 우수한 내열특성을 나타내었다. 또한 VTEOS의 함량이 증가될수록 실리콘 고무의 내유성이 증진되었으며, VTEOS 미첨가 시보다 경도 하락폭이 크게 낮았으며, 파단신율 변화율은 약 2배 이상 감소하였다. 반발탄성도 VTEOS의 함량이 증가될수록 우수하였으며, 압축 영구줄음률 역시 VTEOS가 증가될수록 감소였다. 가교시험 결과 VTEOS가 증가될수록 최대 토크값와 가교밀도가 크게 향상되었다.

The Influence of Recycled Poly(ethylene Terephthalate) Powder on Fatigue Life, Thermal Stability, and Morphology of Halloysite Nanotubes (HNTs) and Precipitated Silica Filled Natural Rubber Composites

Abstract: In this paper, the influence of recycled polyethylene terephthalate powder (R-PET) on fatigue life, thermal properties and micro-fracture surfaces of halloysite nanotubes (HNTs) and silica filled natural rubber composites have been studied. The total amount of hybrid filler in each formulation was kept constant at 20 parts per hundred rubber (phr). The final properties of HNTs/R-PET and Silica/R-PET compounds are considered separately and comparatively. Results indicated that the fatigue life of the natural rubber composites decreased with the replacement of these two fillers by R-PET powder. This observation might be due to the R-PET itself, which reduces the interfacial adhesion and wettability between rubber matrix and fillers. By replacing of HNTs and silica with R-PET powder, the thermal degradation of natural rubber composites was shifted to a lower temperature and the char residues was decreased, in which HNTs/R-PET composites expressed the higher temperature and char residues than silica/R-PET composites. This findings may be due to the HNTs/R-PET has less volatile matter than silica/R-PET that might enhance the degradation temperature of the natural rubber composites. SEM micrographs also exhibited weak interfacial adhesion when these two fillers were replaced with R-PET powder in NR composites.

Preparing precipitated silica, useful as catalyst support, comprises reacting silicate with acid to obtain silica suspension and separating and drying suspension, where addition of silicate and acid is performed according to pH value

Abstract: Preparing precipitated-silica comprises reacting a silicate with an acid to obtain a precipitated silica suspension, and separating and drying the suspension, where the reaction step is carried out by (i) forming an initial aqueous base having a pH of 2-5, preferably 2.5-5, (ii) adding the acid and silicate to the aqueous base until a pH value of reaction medium reaches 2-4, preferably 2.5-5 and (iii) stopping the addition of acid while continuing the addition of silicate in the reaction medium until obtaining the pH value of 7-10, preferably 7.5-9.5. Preparing precipitated-silica comprises reacting a silicate with an acid to obtain a precipitated silica suspension, and separating and drying the suspension, where: the reaction step is carried out by (i) forming an initial aqueous base having a pH of 2-5, preferably 2.5-5, (ii) adding the acid and silicate to the aqueous base until a pH value of reaction medium reaches 2-4, preferably 2.5-5, (iii) stopping the addition of acid while continuing the addition of silicate in the reaction medium until obtaining the pH value of 7-10, preferably 7.5-9.5, (iv) adding the silicate and acid in the reaction medium until the pH value of the reaction medium reaches 7-10, preferably 7.5-9.5 and (v) stopping the addition of silicate while continuing the addition of acid in the reaction medium until obtaining the pH value of less than 6; and the acid comprises sulfuric acid having a concentration of 80 (preferably 90) wt.%, acetic acid or formic acid having a concentration of 90 wt.%, nitric acid having a concentration of 60 wt.%, phosphoric acid having a concentration of 75 wt.% and hydrochloric acid having a concentration of 30 wt.%.